This invention relates to a method of evaluating the soundness of block-like structures (piers, bridge abutments, revetment walls and sea walls, etc.) against collapse as well as to an apparatus for practicing this method.
The piers of bridges are always in danger of being washed away and therefore it very important to establish a simple method of evaluating the soundness of piers against collapse.
A method of evaluating the soundness of piers according to the prior art involves evaluating, by visual inspection, the soundness of all piers against collapse, determining which piers are particularly hazardous based upon the results of evaluation, subjecting these hazardous piers to impact in an impact test by striking them with a heavy cone having a weight on the order of 30 kg, measuring the characteristic frequency produced by this impact and evaluating the soundness of the piers against collapse on the basis of a change in the characteristic frequency.
Visual inspection depends upon the individual experience of the inspector and a change in condition that can be identified by visual inspection usually has progressed to a considerable degree. In addition, abnormalities are sometimes overlooked and internal faults sometimes cannot be found. Furthermore, the foundation of a pier cannot be checked by direct visual inspection if the foundation is submerged in water or buried in the ground.
The impact test not only involves the danger that the pier per se and the structure supporting it will be damaged but also requires that care with regard to the surrounding structures and caution with respect to inspection personnel. Moreover, since a large-scale apparatus is required, locations that can be inspected are limited and preparations take time, the latter limiting the amount of time that can be spent on inspection. As a consequence, it is difficult to inspect all piers.
Thus, visual inspection depends too much upon personal experience, abnormalities can go unnoticed and internal faults may not be discovered. The impact test involves risk of damage to structures and injury to inspection personnel and there are limitations in terms of locations that can be inspected and inspection time. This makes it difficult to inspect a large number of locations.